In an engine of a vehicle, a mixture of air inflowing from the outside and a fuel is combusted at an appropriate ratio to generate a power.
In a process of generating the power by driving the engine, the external air for the combustion must be appropriately supplied to obtain a desired output and combustion efficiency. After the combust for the power generation of the engine, an exhaust gas is generated and then this exhaust gas is exhausted to an outside.
Further, a nitrogen oxide (NOx) included in the exhaust gas is regulated as an atmospheric pollution source and there has been an effort to lessen exhaust of NOx.
An exhaust gas recirculation (EGR) system has been provided to a vehicle for reducing noxious exhaust gas. Generally, NOx is increased in a case where an air-fuel ratio of an air-fuel mixture is high, which is necessary for sufficient combustion. Thus, the exhaust gas recirculation system mixes exhaust gas from an engine with the air-fuel mixture, for example at 5-20%, thereby reducing the amount of oxygen in the air-fuel mixture and obstructing combustion, and so lessening generation of NOx.
As a representative exhaust gas recirculation system in a related art, there is a low pressure exhaust gas recirculation (LP-EGR) apparatus. The low pressure EGR apparatus recirculates the exhaust gas into an intake pathway.
However, the exhaust gas that is recirculated by the exhaust gas recirculation system generally has high temperature and humidity. Accordingly, when the recirculate exhaust gas of high temperature and inflowing fresh air of low temperature are mixed, condensed water is generated in an intake manifold. In this case, the generated condensed water has very high acidity due to various harmful components contained in the exhaust gas.
Further, there is a problem that peripheral parts to which the exhaust gas flows were corroded by the condensed water of high acidity, if the condensed water inflows to the combustion chamber of the engine, a problem that the combust becomes unstable is generated.
Additionally, In regions where the temperature is low, when the generated condensed water is frozen in the intake manifold, there may be a problem that each intake pathway connected with each combustion chamber is clogged.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.